Poly(1,4-butylene terephthalate) resin is widely used in molding compositions due to its many excellent properties, i.e. strength, solvent resistance, etc. Of growing importance, are applications which require that this resin also have good electrical properties. In such applications, the molded parts may be exposed to severe conditions, such as exposure to electrical discharge or to excessive leakage current across its surface. These conditions require not only that the molded part have flame resistance, but also that the molded part have a high degree of resistance to carbonization i.e. good track resistance and a high degree of resistance to electrical discharge, i.e. good arc resistance.
However, it has been a problem that flame retarded poly(1,4-butylene terephthalate) resin has very poor track resistance compared to the non-flame retarded resin. U.S. Pat. No. 4,000,109, Smith, et al, use a metal borate to improve track resistance in flame retarded poly(1,4-butylene terephthalate) resin. U.S. Pat. No. 4,421,888, Okada, disclose a flame retarded, talc and glass fiber reinforced, polyester blend having a sustained high track resistance. Obviously, it is desirable to have flame retarded polyester blends having a greater degree of track resistance.
Therefore, it is an object of the present invention to provide flame retarded thermoplastic poly(1,4-butylene terephthalate) resin molding compositions, articles molded from which have good track resistance.
It is a further object of the present invention to provide flame retarded, glass fiber reinforced, poly(1,4-butylene terephthalate) resin molding compositions, likewise, articles molded from which have good track resistance.